Circular No. 8255
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)COMET 104P/KOWAL
On 1973 Jan. 14, the Central Bureau received a cablegram with the
following two-line message from the late L. Boethin, Abra, Philippines
(cf. IAUC 2745): "new comet january 11 20:00 ut in 11h 38m" and "20s 9m 5
moving sse 8 minutes a day". Although there was uncertainty as to whether
the "20s" referred to the seconds of time of R.A. or to the fact that the
Decl. was "20 deg south" (for otherwise the Decl. information was absent),
visual searches were conducted at the request of the Bureau to mag 13 over
the general range 11h < R.A. < 12h, +3 deg > Decl. > -30 deg. The searches
were unsuccessful, and Boethin did not respond to a cabled request that he
verify the Bureau's interpretation of his cablegram. A letter received by
the Bureau on Jan. 29 showed that "20s" did refer to the seconds of R.A.
but that, by chance, the Decl. really was -20 deg; the magnitude was given
as 9.5, so that, if the comet existed, the confirmation attempts ought to
have revealed it. The letter also mentioned that the coma was large and
diffuse, 8' in diameter, with a small distinct nucleus. It included the
following three positions (made visually with a 0.20-m reflector and converted
here to equinox 2000.0) and was dated and timed coincidentally with the
third observation:
1973 UT R.A. (2000) Decl.
Jan. 11.833 11 40 52 -20 29
12.833 11 41 01 -20 37
13.833 11 41 10 -20 45
In a special-delivery letter dated Feb. 11, Boethin added that he had
observed the comet again "on Monday" (presumably on Jan. 14.8 UT) but that it
had by then "darkened considerably", to "about mag 12-13!". "On Tuesday" the
bright moon (it was full on Jan. 18.9 UT) prevented further observations.
G. Kronk, Troy, IL, who was in communication with Boethin in the 1980s
concerning the latter's several unconfirmed comets (Marsden and Roemer 1978,
Quart. J. Roy. Astron. Soc. 19, 64), has recently suggested that the 1973
object might have been comet 104P. At that time, some months after the
perihelion passage (T = 1972 Aug. 4) preceding that of its 1979 discovery,
comet 104P would not have been expected to be brighter than mag 17.
However, the nongravitational forces affecting this comet are unusually
large and variable (indeed, it was necessary to incorporate them in a linkage
of the first two apparitions, as well as for the 1997-2003 linkage), a
circumstance well known to be associated with outbursts (and
splitting). Nevertheless, a nongravitational solution reasonably fitting
the 1979-1998 observations does represent Boethin's three rough
positions within 2', so the identification is secure.
(C) Copyright 2003 CBAT2003 December 11 (8255) Brian G. Marsden